An exhaust gas analyzer for analyzing exhaust gas exhausted from an engine of a vehicle or the like is used in arrangement in each of a plurality of test chambers. In each of the test chambers, an engine of such as a vehicle serving as a specimen is installed.
Then, in the case of calibrating these exhaust gas analyzers, it is necessary to supply calibration gas for zero calibration or span calibration to flow through the exhaust gas analyzers. In this arrangement, since a calibration gas cylinder storing the calibration gas is in a state of high pressure, the calibration gas cylinder is usually provided in a gas cylinder chamber separated from the test chambers. In addition, since the calibration gas is supplied to a plurality of exhaust gas analyzers from the calibration gas cylinder in common, the number of calibration gas cylinders is reduced.
However, in the conventional case where the calibration gas is concurrently supplied from one calibration gas cylinder to a plurality of exhaust gas analyzers to be calibrated, calibration time is uniformly set for all of the exhaust gas analyzers. In addition, during this calibration time, it is configured to render the calibration gas to flow into all of the exhaust gas analyzers.
In this arrangement, a time until an output value of each exhaust gas analyzer becomes stable is different depending on a length of a calibration gas pipe between the calibration gas cylinder and the exhaust gas analyzer and a status of a contact gas surface of the calibration gas pipe or piping conditions such as a material of the calibration gas pipe and a situation of such as an installation environment of each of the exhaust gas analyzers. For example, in an exhaust gas analyzer having a lengthy pipe from the calibration gas cylinder, it takes a long time for the calibration gas to reach the exhaust gas analyzer so that the time to stabilize the output value of the exhaust gas analyzer is accordingly increased. Moreover, as described above, in the case where the calibration time is uniformly set for all of the exhaust gas analyzers, it is necessary also for an exhaust gas analyzer having completed with the calibration with the output value already stabilized to wait for a lapse of the calibration time, and there arises a problem that a start of a measurement of the exhaust gas using the exhaust gas analyzer is delayed. Furthermore, in spite that the calibration can be early finished for the exhaust gas analyzer having completed with the calibration with the output value already stabilized, the calibration gas is unnecessarily continued to flow into the exhaust gas analyzer, and there arises also a problem that the calibration gas is consumed in waste.